Method and apparatus for multi-carrier/multi-cell discontinuous reception (DRX)/discontinuous transmission (DTX) operations and activation/deactivation of DRX/DTX are disclosed. A wireless transmit/receive unit (WTRU) may configure at least one state variable for controlling DRX, DTX or both on a group of cells. The WTRU may receive an order for DRX or DTX activation or deactivation. The WTRU may determine a setting for the state variable based on the order. The WTRU may activate or deactivate DRX or DTX based on the setting for the state variable. The group of cells may include all cells within the same frequency band, all cells in a particular frequency or group of frequencies, and all secondary cells associated with a primary cell. The primary cell may be an uplink (UL) or downlink (DL) primary cell. The secondary cells may be UL or DL secondary cells. The WTRU may apply common, group-specific or cell-specific DRX monitoring.